These studies are designed to examine the physiology mononuclear leukocytes and their roles in host defense against tumors and bacterial pathogens. Four specific research projects are planned. 1) Studies of the mobility of Fc and complement receptors on mouse mononuclear phagocytes. Substrate adherent ligands are used in these studies to promote receptor movement. Monoclonal anti-receptor antibodies are employed to measure the speed and extent of receptor movement. Monoclonal anti-receptor antibodies are employed to measure the speed and extent of receptor movement from the cells' upper surface. 2) Energetics of phagocytosis. The role of creatine phosphate in macrophage energy metabolism is being examined. Heat production by phagocytosing macrophages, as measured by differential scanning microcalorimetry, is also under study. 3) Immunobiology of Legionnaires' disease. The Legionnaires' disease bacterium grows in human monocytes and their growth in monocytes is not inhibited when the bacteria are coated with antibodies and complement. Studies of the role of cell mediated immunity in inhibiting the growth of this bacterium are planned. 4) Tumoricidal effects of activated macrophages. Macrophages activated by bacterial adjuvants have the capacity to destroy tumor cells in vivo. Studies are directed toward resolving the ways monocytes reach the tumor bed and are activated in vivo.